Prehospital Manual Ventilation: An NAEMSP Position Statement and Resource Document

Abstract

Manual ventilation using a self-inflating bag device paired with a facemask (bag-valve-mask, or BVM ventilation) or invasive airway (bag-valve-device, or BVD ventilation) is a fundamental airway management skill for all Emergency Medical Services (EMS) clinicians. Delivery of manual ventilations is challenging. Several strategies and adjunct technologies can increase the effectiveness of manual ventilation.

NAEMSP recommends:

• All EMS clinicians must be proficient in bag-valve-mask ventilation.

• BVM ventilation should be performed using a two-person technique whenever feasible.

• EMS clinicians should use available techniques and adjuncts to achieve optimal mask seal, improve airway patency, optimize delivery of the correct rate, tidal volume, and pressure during manual ventilation, and allow continual assessment of manual ventilation effectiveness.

Key words:

• bag-valve-mask
• manual ventilation
• EMS
• airway management

Introduction

Manual ventilation involves delivering positive pressure ventilation using a self-inflating bag device attached either to a facemask (bag-valve-mask, or BVM) or an invasive airway device (bag-valve-device, or BVD) such as a supraglottic airway (SGA) or an endotracheal tube. Manual ventilation is a challenging skill, particularly when delivered via BVM due to the difficulty of maintaining an adequate seal between the patient’s face and the mask. Although BVM ventilation is often regarded as “basic,” Emergency Medical Services (EMS) clinicians must train to achieve competency.

Importance of Proficiency with Bvm

All EMS Clinicians Must Be Proficient in Bag-Valve-Mask Ventilation.

BVM ventilation is a fundamental resuscitation skill and the primary method for providing assisted ventilations to patients with respiratory failure (1). In addition, advanced airway management techniques such as endotracheal intubation (ETI) or SGA insertion may be difficult or impossible in select situations (2). Two recent prehospital clinical trials by Wang et al. and Benger et al. demonstrated intubation failure rates in up to 44% of cases (3, 4). Success rates are higher for insertion of SGAs, but still not 100% (4–6). Therefore, even if trained in advanced airway insertion, EMS clinicians must be skilled at BVM ventilation (2, 7).

BVM ventilation plays an important adjunctive role when it is used for initial stabilization and preoxygenation while the EMS clinician prepares for advanced airway insertion and also when used to re-oxygenate the patient between advanced airway insertion attempts. After endotracheal tube or SGA insertion, EMS clinicians must continue to provide manual ventilation using the BVD technique until the invasive airway can be attached to a mechanical ventilator.

Because of its key role in resuscitation, EMS clinicians must possess exceptional BVM skills. Although considered a ‘basic’ skill, BVM is challenging at least 15% of patients (2, 8–12). Inadequate mask seal and excessive resistance to entry or exit of air from the lungs can all contribute to challenging BVM ventilation. Langeron et al. found that age over 55 years, body mass index greater than 26 kg/m², lack of teeth, presence of beard, and history of snoring are associated with difficult BVM ventilation (8). Kheterpal et al. confirmed similar criteria in their cohort of over 20,000 cases of BVM use (13). Furthermore, difficult BVM ventilation is more common in patients who are also difficult to intubate (2, 8, 11, 14). In addition to these patient-based factors, the EMS environment presents other challenges that make BVM difficult including: limited availability of personnel, the need for EMS clinicians to provide care in suboptimal settings, and rescuer and patient positioning challenges.

EMS clinicians must have the training and resources to attain the highest level of competence in BVM ventilation. The American Heart Association (AHA) recognizes that “bag-mask ventilation is a challenging skill that requires considerable practice for competency” (15). Initial and ongoing training are essential to ensure competency in BVM ventilation (16–18). Proper BVM technique must achieve not only adequate mask seal and airway patency but also the delivery of ventilations at the correct rate, volume, and pressure. Training is essential to mitigate inadvertent hyperventilation, which leads to increased airway management complications, such as regurgitation and aspiration of gastric contents due to insufflation of the stomach and may be associated with worse patient outcomes (19–23). By reducing these complications, proper BVM ventilation can also increase success with advanced airway placement, thereby optimizing airway management.

Two-person Bvm Ventilation

BVM Ventilation Should Be Performed Using a Two-Person Technique Whenever Feasible.

Whenever possible, EMS clinicians should perform BVM ventilation using a two-person technique, with one rescuer maintaining a two-handed mask seal and the other managing bag insufflation. Maintaining an adequate seal while opening the airway is one of the most difficult aspects of BVM ventilation. The chaotic and uncontrolled environment of field resuscitations is likely to make one-person BVM ventilation even more difficult and increase the need for modifications that improve success. Two-person BVM technique ensures that one operator can maintain a two-hand mask hold, which increases the mean tidal volume delivered for both adult and pediatric patients (24–30). Further evidence of the importance of a two-handed mask grip is provided by Elling and Politis who demonstrated that more than half of EMS clinicians were not able to provide effective ventilations when operating the BVM alone and that a two-hand grip with a pocket mask outperformed use of a BVM with a one-handed mask seal (31). Multiple studies in the operating room and simulation settings illustrate the difficulty of BVM ventilation performed by a single clinician, as well as the superiority of the two-person technique in delivering consistent tidal volumes (24–29). Hess and Baran found tidal volumes delivered by one person to be less than half that delivered with a two-person BVM, mouth-to-mouth, or mouth-to-mask ventilation technique (24). In a simulated cardiac arrest resuscitation with two EMS clinicians, Gerber et al. found improved CPR quality and higher tidal volumes that were closer to the target range using two-person manual ventilation where one rescuer maintained a two-handed mask seal and the other rescuer performing chest compressions squeezed the resuscitator bag during the pause for ventilations (27).

Techniques to Improve Manual Ventilation

EMS Clinicians Should Use Available Techniques and Adjuncts to Achieve Optimal Mask Seal, Improve Airway Patency, Optimize Delivery of the Correct Rate, Tidal Volume, and Pressure during Manual Ventilation, and Allow Continual Assessment of Manual Ventilation Effectiveness.

Because of its complexity, EMS clinicians should use all available modalities to optimize mask seal, improve airway patency, and control rate, volume, and pressure of manual ventilation. Figure 1 summarizes these elements.

Figure 1. Components of optimal bag-valve-mask (BVM) ventilation.

Image credit: J Lyng, MD

Mask Seal

Using a two-hand mask hold is superior to one-hand technique and is the best way to optimize mask seal (28–30). Classic BVM technique involves holding the mask to the face with the rescuer’s fingers in the “E-C” configuration. However, an alternate two-handed technique uses the thenar eminence to grip the mask. While a matter of personal preference, the two-handed thenar eminence technique may have advantages for those with smaller hands or in patients for whom achieving adequate seal is challenging. Gerstein et al. found the two-handed thenar eminence grip to be superior to E-C technique in novice operators (32). Otten et al. found that women achieved better seal using the two-handed thenar eminence hold; a difference that may be related to rescuer hand size relative to the mask (30). Soleimanpour demonstrated successful ventilation using a combination of the two holds (33).

Given the realities of EMS operations, only a single rescuer may be available on scene to provide ventilations. Uhm and Kim evaluated the effect of variations of the one-handed E-C grip technique and found that the longer the distance between the fingers forming the “C” portion of the mask grip, the stronger the mask seal, the higher the peak pressure, and the higher the delivered tidal volume (34). Umesh et al. proposed an alternate E-O hold on the traditional face mask, where the operator encircles the mask neck with the first two digits and remaining digits provide the chin lift. The authors found improved mask seal using this technique compared to the E-C mask hold in both a manikin study and a randomized blinded cross-over study in the operating room (35, 36). Soleimanpour also found the E-O technique to be superior among novices (37). Figure 2 illustrates these various one- and two-handed mask grip techniques.

Figure 2. BVM mask-grip techniques. (A) One-handed E-C grip, (B) One-handed E-O grip, (C) Two-handed E-C grip, (D) Two-handed thenar eminence grip.

Image credit: J Lyng, MD

In addition to grip technique, other considerations such as the material of the mask may influence effectiveness of the seal (38). A modified BVM with integrated handle to allow a single rescuer to maintain the two-handed mask seal while simultaneously squeezing the bag has demonstrated conflicting results (39, 40). Other modifications, including use of a more ergonomically-designed mask have been described, however these masks are not typically available in EMS systems and, to our knowledge, have not been studied in the prehospital environment nor compared directly to the two-hand mask hold techniques (17, 41).

Certain patients present particular challenges to maintaining an adequate seal for effective BVM ventilation. In bearded patients it is difficult to maintain a seal due to leaks between the hair and the mask edge (8). Althunayyan et al. used gel applied to the beard to significantly improve delivered tidal volumes (median 467 ml vs. 283 ml, p < 0.01) and the number of successful ventilations (42). Researchers have suggested leaving dentures in place in endentulous patients (8). Golzari et al. found that placing gauze into each buccal space resulted in the highest rate of successful ventilations with BVM in edentulous patients, followed by maintaining dentures in place (43). While potentially helpful, none of these techniques have been rigorously tested.

Airway Patency

Airway obstruction frequently occurs in the unconscious or obtunded patient due to decreased muscular tone in pharyngeal muscles and consequent obstruction at the level of the soft palate, posterior oropharynx, epiglottitis, and tongue (44, 45). Therefore, BVM technique also involves simultaneous positioning of the head and neck to open the airway structures. The basic maneuvers to establish an airway include putting the patient in the “sniffing position” to align the three important airway axes (mouth, laryngeal, and pharyngeal). Safar found that neck flexion obstructed the airway in 80 anesthetized, spontaneously breathing patients; and neck extension (chin up) position achieved patency in 50% of this group, while the other 50% required either anterior displacement of the mandible, insertion of an oral airway, or both to achieve airway patency (46). Boidin showed that epiglottic obstruction was common and could be overcome by anterior displacement of the hyoid with elevation of the occiput in a range from 4 cm to 8 cm above horizontal, with head tilt contributing less relief of obstruction than elevation of the occiput (45) .

Oropharyngeal and nasopharyngeal airways may be used to displace obstructing tissues. They are well-accepted adjuncts in airway management, but their relative and comparative efficacy have not been rigorously studied. Studies by Safar and Boidin, confirmed nasopharyngeal airways displaced the obstructing epiglottitis in some patients (45, 46). Still, EMS clinicians must carefully assess the effectiveness of the airway adjunct after placement, since a poorly positioned or incorrectly sized adjunct has the possibility to negatively affect airway patency. Both Roberts and Stoneham found that, if placed too deeply, nasopharyngeal airways can displace the epiglottis, thereby paradoxically causing an airway obstruction (47, 48). Kim et al. evaluated a range of oral airways by fiberoptic bronchoscopy in males and females undergoing routine operative procedures and found that optimal oral airway size was defined by the tip of the device positioned close to, but not touching the epiglottis; devices too large could pass the epiglottis possibly leading to airway injury (49). Despite these potential rare issues, given the inherent challenges in providing effective BVM ventilation, routine use of one or more of these adjuncts is good practice. In a retrospective review of a small cohort of in-hospital cardiac arrests at a Japanese teaching hospital, Yamada et al. found that BVM ventilation performed with an airway adjunct was associated with good neurologic outcome, defined as cerebral performance category (CPC) of 1, (OR 3.52, 95%CI 1.07–11.5), but that other airway management techniques including BVM alone and ETI were not (50).

Rate and Volume

Both BVM and BVD strategies of manual ventilation require the EMS clinician to deliver manual ventilation at the appropriate rate and volume for the patient’s clinical condition. Distractions in the prehospital environment can draw an EMS clinician’s attention away from providing high-quality manual ventilation, leading to inadvertent hyperventilation. Both over-ventilation and insufficient ventilation can be detrimental to patient outcomes (51). The AHA guidelines recommend an adult ventilation rate of 10 breaths per minute with tidal volumes of 500–600 mL, and a pediatric rate of 20–30 breaths per minute (with no pediatric-specific tidal volume recommendation), while also specifically highlighting the need to avoid excessive ventilation (52). Other sources recommend pediatric tidal volume of 6–7 ml/kg, though it is likely difficult to deliver this specifically calculated volume using a bag-valve device (53). Unfortunately using chest-rise is not an effective method to assess delivery of adequate tidal volume during manual ventilation of pediatric patients (54).

Several studies have demonstrated that EMS and hospital-based clinicians manually ventilate patients with rates as high as 50 ventilations per minute (19, 20, 31, 55–60). In a study by Scott et al. only 42.3% of clinicians delivered tidal volumes at the target 5–8 ml/kg of ideal body weight and the majority of participants exceeded 20% variability among breaths (61). There are harmful physiologic effects of hyperventilation including increased intrathoracic pressure, decreased cerebral blood flow, impaired coronary perfusion pressure, barotrauma, and gastric insufflation increasing the risk for aspiration (20, 23, 62). Together these harmful effects have been shown to increase morbidity and mortality, particularly for patients with cardiac arrest and traumatic brain injuries (19, 20, 63).

Timing and Feedback Devices

Several studies have evaluated whether use of a metronome, cadence, or feedback device can prevent inadvertent hyperventilation in a simulated environment. While not addressed in the most recent AHA guidelines, AHA previously noted “indirect evidence that monitoring respiratory rate with real-time feedback is effective in avoiding hyperventilation and achieving ventilation rates closer to recommended values” (64). Metronomes including those with voice prompts improved achievement of ventilation targets, whereas visual timing did not affect rate (65–67). The use of combined visual prompts with real-time visual feedback plus mask-leak and rate alarms improved compliance with ventilation goals (68).

Resuscitation Bag Size

Wenzel et al. demonstrated a significant decrease in gastric insufflation volumes when comparing adult manual ventilation using a pediatric BVM and an adult BVM in a bench model (69). Additional studies by Doerges et al., Siegler et al., Dafilou et al., and Nehme & Boyle also support the use of pediatric bags, those that typically deliver volumes of 450-650 mL (total resuscitator bag volumes are 500–1000 mL), to provide manual ventilation to adult patients in order to achieve more consistent tidal volumes within the target range (70–73). Furthermore, studies by Kroll and Zweiker evaluated bag grip technique and its effect on delivered tidal volume during manual ventilation; reducing the digits used to squeeze the bag increased the proportion of ventilations delivered at target volumes (74, 75). Evaluations of the ideal bag-volume for pediatric manual ventilation have not yet been published.

Pressure, Manometers, and PEEP

Standard resuscitation bags may encourage excessive peak flow rate and peak inspiratory pressure (PIP), and thereby increase the risk of gastric insufflation as well as barotrauma (76). Wenzel et al. employed a manikin model of variable esophageal sphincter tone to demonstrate the association between larger tidal volumes and larger gastric insufflation volumes (69). In a simulated cardiac arrest, Lacerda et al. noted that manometers on self-inflating bags are associated with better control of PIP (77).Multiple investigators have demonstrated that the use of “smart” self-inflating ventilation bags significantly decrease inspiratory flow rate, PIP, and gastric insufflation volume (78–80). Smaller sized bags have also been shown to improve compliance with PIP targets in addition to their improvement in target volume (71, 73).

Positive end expiratory pressure (PEEP) can improve oxygenation and may also decrease atelectrauma (62, 81). PEEP can also increase intrathoracic pressure which negatively impacts circulation via reduction of venous return and increase of right ventricular afterload, however in most cases the benefits of controlled PEEP appear to outweigh the harms (82). As long as clinicians maintain a good mask seal with BVM or are performing BVD ventilation, PEEP can be delivered by attaching a commercially available adjustable valve to a standard self-inflating bag. PEEP valves should be made available to EMS clinicians as part of an overall airway management strategy.

Assessing Ventilation Quality

While ongoing assessment of the effectiveness of manual ventilation is essential, there are presently few validated prehospital methods to verify ventilation quality. Precise assessment of ventilation tidal volume and rate requires use of a closed circuit with an appropriate sensing device, for example, a spirometer. However, there are currently no widely available portable devices appropriate for prehospital use. It is also difficult in the prehospital environment to maintain the mask seal needed to achieve a closed circuit. In addition, sensing technology must be applied to the BVM device; this is not currently routine practice for EMS.

In the absence of suitable technology, subjective and objective measures are commonly used as a surrogate for ventilation quality. For example, physical exam (observation of chest rise and auscultation of lung sounds) is often taught as the basic method for verifying delivery of ventilation. However, only limited data describe the accuracy of physical assessment. Lung sounds may be difficult to appreciate in the uncontrolled field environment, especially during chest compressions. In neonates, Pouton et al. demonstrated that clinicians had difficulty assessing chest movement and that agreement between clinician estimates and measured exhaled tidal volume was poor (83).

Pulse oximetry depends upon perfusion and therefore is of limited value as a measure of effective manual ventilation (84–86). Unfortunately, this distinction is not always clear to EMS clinicians, and some clinicians may over-rely on pulse oximetry to guide their ventilation techniques (87, 88). As an example, Mumma et al. found that novice clinicians increased their ventilation rates when pulse oximetry values were not visible, but experienced clinicians maintained their rates of ventilation under the same conditions (89). Further, cessation of ventilation may not be reflected by pulse oximetry for up to two minutes, making it a poor metric for assessment of ventilation (90).

Capnography provides the best currently available method to detect manual ventilations. The depicted amplitude of the capnograph waveform may be a reasonable surrogate for exhaled tidal volume, but two factors can influence this relationship: 1) inadequate perfusion, in which case the exhaled carbon dioxide level may be low; and 2) incomplete mask seal, such that exhaled air leaks around the mask, circumventing the ETCO₂ sensor. Several systematic reviews concluded that ventilation could be improved with direct feedback including use of capnography (91, 92). Vithalani et al. performed a retrospective review of manual ventilation and found that EMS clinicians failed to recognize cases of ineffective ventilation; 8.4% of attempts to provide manual ventilation were not recognized as ineffective by EMS clinicians but were identified as ineffective during review of capnography waveforms (93).

Future Research

Additional studies are needed to direct how best to train EMS clinicians to attain and maintain competency in manual ventilation. Current studies on one- versus two-person BVM and mask grip techniques are limited to simulated or operating room environments with process outcomes. Studies are needed to evaluate patient-centered outcomes during actual patient resuscitations, to validate the use of ETCO₂ as a marker for ventilations of sufficient tidal volume, and to correlate ETCO₂ amplitude with specific tidal volumes. Further innovations to improve manual ventilation, including devices to guide the EMS clinician to deliver the optimal manual ventilation for the individual patient, are imperative. New technologies are needed to facilitate real-time measurement of ventilation quality and tidal volume. Finally, preliminary data suggest that the FIO2 delivered by self-inflating resuscitation bags from different manufacturers is inconsistent, and further studies are needed to understand the effects of various resuscitator bags on delivery of oxygen during manual ventilation(94).

Conclusion

Manual ventilation, especially using a BVM technique, is a challenging but basic skill that all EMS clinicians must master. Strategies to imporove success when using a BVM approach include using a two-person technique, two-handed mask seal, and airway patency adjuncts. For both BVM and BVD approaches, use of volume-restricted bags for adult patients and use of PEEP both adult and pediatric patients are recommended, and use of timing devices may also have utility. Continued research is needed to identify strategies to objectively confirm quality of manual ventilation and to identify the optimal manual ventilation strategies and technology for both adult and pediatric patients.